2 Aurigae
Possible binary star system in the constellation Auriga
From Wikipedia, the free encyclopedia
2 Aurigae is a possible binary star system in the northern constellation of Auriga. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of +4.79.[2] It forms an attractive four-star asterism when viewed in a low power eyepiece, together with the nearby HIP 22647 and another very loose visual pair, HIP 22776 and HIP 22744, all above magnitude 8. 2 Aurigae is moving closer to the Earth with a heliocentric radial velocity of −17 km/s.[4]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Auriga |
| Right ascension | 04h 52m 37.98035s[1] |
| Declination | +36° 42′ 11.4771″[1] |
| Apparent magnitude (V) | +4.79[2] |
| Characteristics | |
| Evolutionary stage | red giant branch[1] |
| Spectral type | K3- III Ba0.4[3] |
| Apparent magnitude (G) | 4.28[1] |
| B−V color index | 1.414±0.003[4] |
| Astrometry | |
| Radial velocity (Rv) | −17.24±0.08[4] km/s |
| Proper motion (μ) | RA: −25.273±0.125[1] mas/yr Dec.: −3.715±0.098[1] mas/yr |
| Parallax (π) | 5.2978±0.1192 mas[1] |
| Distance | 620 ± 10 ly (189 ± 4 pc) |
| Absolute magnitude (MV) | –1.84[2] |
| Details | |
| Mass | 2.86[5] M☉ |
| Radius | 48.14+0.83 −1.79[6] R☉ |
| Luminosity | 599±29[6] L☉ |
| Surface gravity (log g) | 1.79[7] cgs |
| Temperature | 4,115+79 −35[6] K |
| Metallicity [Fe/H] | −0.24±0.03[4] dex |
| Rotational velocity (v sin i) | 2.3[7] km/s |
| Age | 1.80[5] Gyr |
| Other designations | |
| 2 Aur, BD+36°952, FK5 1201, HD 30834, HIP 22678, HR 1551, SAO 57475, Gaia DR3 198271397081746560[8] | |
| Database references | |
| SIMBAD | data |
The visible component is an aging giant star with a stellar classification of K3- III Ba0.4.[3] The suffix notation indicates this is a mild barium star, which means the stellar atmosphere is enriched with s-process elements. It is either a member of a close binary system and has previously acquired these elements from a (now) white dwarf companion or else it is on the asymptotic giant branch and is generating the elements itself.[9] 2 Aurigae is 1.80[5] billion years old with 2.86[5] times the mass of the Sun and has expanded to 48[6] times the Sun's radius. It is radiating 599[6] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,115 K.[6]